Seattle Labor Day forecast: So long summer

Snow in the mountains, cold in the lowlands for Labor Day

BY LEVI PULKKINEN, SEATTLEPI.COM STAFF

Published 12:05 pm, Thursday, September 3, 2015

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This National Weather Service chart shows temperatures in Seattle so far this September. The dark blue bars represent temperatures in the first two days of September. The green portion shows the normal temperature range for Seattle, while the red and blue bars show the historic high and low temperatures. less

This National Weather Service chart shows temperatures in Seattle so far this September. The dark blue bars represent temperatures in the first two days of September. The green portion shows the normal ... more

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An airplane tanker flies through smoky air as it drops fire retardant on a wildfire that flared up in the late afternoon near Omak, Wash., Thursday, Aug. 27, 2015. Firefighters were holding their own Thursday against the largest wildfire on record in Washington state, even as rising temperatures and increased winds stoked the flames. less

An airplane tanker flies through smoky air as it drops fire retardant on a wildfire that flared up in the late afternoon near Omak, Wash., Thursday, Aug. 27, 2015. Firefighters were holding their own Thursday ... more

Photo: Ted S. Warren, AP

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The present El Nino, could be the strongest on record. The red and yellow bands represent warmer than usual weather near the equator.

The present El Nino, could be the strongest on record. The red and yellow bands represent warmer than usual weather near the equator.

Photo: Earth.nullschool.net

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These false-color images provided by NASA satellites compare warm Pacific Ocean water temperatures from the strong El Nino that brought North America large amounts of rainfall in 1997, left, and the current El Nino as of Aug. 5, 2015, right. Warmer ocean water that normally stays in the western Pacific, shown as lighter orange, red and white areas, moves east along the equator toward the Americas. Forecasters say this El Nino is already the second strongest on record for this time of year and could be one of the most potent weather changers in 65 years. (NASA via AP) less

These false-color images provided by NASA satellites compare warm Pacific Ocean water temperatures from the strong El Nino that brought North America large amounts of rainfall in 1997, left, and the current El ... more

Photo: AP

Seattle Labor Day forecast: So long summer

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It’s beginning to look a lot like … well, not Christmas, exactly. September-uary?

Seattle’s endless summer appears to have come to a close, though, with the Weather Service predicting that highs will barely hit 70 in Seattle over the holiday weekend. Snow showers have arrived in the high country and there’s no warmer weather on the horizon.

The Weather Service warns that a cold weather system will drive snow levels down to 5,500 feet in the Cascades and Olympics. Up to 6 inches of snow could fall at higher elevations. Thundershowers and hail are possible in Skagit and Whatcom counties.

September has been colder than usual, with lows in the low 50s. In Seattle, the record lows range from 44 degrees to 48 degrees in early September.

The highs have come short of normal. Wednesday’s high was 68 degrees, six degrees short of normal. The record high for Thursday is 93 degrees.

Cooler weather comes after an unusually warm winter, spring and summer for Western Washington. Seattle’s first high temperature record of the year fell in March, and the records kept coming through late August.

Meteorologists are predicting a strong El Nino, the strongest in the past half century.

In a statement Tuesday, the World Meteorological Organization warned that meteorologists aren’t sure how changes equatorial Pacific Ocean will impact the world’s weather given the climate change.

“This is a new planet. Will the two patterns reinforce each other or cancel each other?" said David Carlson, director of WMO's World Climate Research program, according to the Associated Press. "We have no precedent for this situation."

Models indicate ocean temperatures in the east-central tropical Pacific are likely to reach peaks that could make this El Nino among the four strongest since 1950. Peak strength is expected between October and January.

A strong El Nino usually means a wetter winter for Washington, and has historically delivered a deeper than usual snowpack. That of course depends on the extra precipitation falling as snow.